Two doses (10 or 150 mg/kg) of crude marihuana extract were administered (p.o.) daily to pregnant rats throughout gestation. One group of control animals received vehicle administrations and was pair-fed to drug-treated animals. A second group was not treated and was fed ad lib. At birth, all offspring were removed from their biological mothers and were fostered to nondrug-treated surrogate mothers. Marihuana reduced maternal weight gain during pregnancy and produced a dose-related decrease in body weight of offspring at birth. This decreased body weight was also evident at 11 weeks of age. Behavioral studies conducted thus far have shown a significant initial impairment of ability to remain on a roto-rod on the part of the female offspring prenatally exposed to marihuana. In addition, these offspring do not attain the peak level of performance exhibited by control animals. No differences between drug-treated animals and controls has thus far been observed in shock avoidance or brightness discrimination learning, spontaneous alternation, or open field behavior.